What did Henry M. Sheffer show about the Sheffer stroke?

In 1913, the American logician Henry M. Sheffer demonstrated that all truth-functional connectives in propositional logic can be defined using a single connective, now known as the Sheffer stroke.1

This connective, which functions as a negated conjunction, allows for the construction of complex logical propositions without the need for multiple distinct operators like "and" or "or". His work highlighted the interdefinability of logical connectives, showing that a single, sufficient operator is capable of expressing the full range of truth-functional dependencies.1